Subject: Re: DEC 21x4x ethernet driver in 100baseTX mode
To: Matthias Scheler <>
From: Matt Thomas <>
List: current-users
Date: 10/03/1997 05:28:45
At 03:47 AM 10/3/97 +0200, Matthias Scheler wrote:
>	Hi,
>can anybody enlight me what this means?
>Oct  3 03:11:53 colwyn /netbsd: de0: abnormal interrupt: transmit underflow (raising TX threshold to 1024)
>Oct  3 03:12:07 colwyn /netbsd: de0: abnormal interrupt: transmit underflow (switching to store-and-forward mode)

it means that your system isn't capable of supplying transmit data 
quickly enough and the 21x4x transmit fifo became emtpy.  The driver
then increases the transmit threshold to a higher value until it
finally gives up and switches into store-and-forward mode (which might
be a bit slower since the entire packet must be dma'ed into the fifo
before transmit starts.)
Matt Thomas               Internet:
3am Software Foundry      WWW URL:
Nashua, NH                Disclaimer: I disavow all knowledge of this message